Low Complexity Acquisition and Tracking Methods for CSK Modulated Signals

Abstract

In order to meet the demand of high-precision positioning, GNSS PPP service needs to broadcast the precise correction message frequently. The required data rate is usually above 500 bps, which is significantly higher than the 50 bps rate of the traditional GNSS signal. Therefore, QZSS L6 signal adopts CSK modulated signal. CSK modulated signal has become an important candidate for GNSS signal with high data rate. Compared with the BPSK signal, CSK modulated signal uses code phase to carry data bits, and can flexibly increase the data rate while keeping the code period unchanged. However, the existing CSK modulated signal is mainly used for data transmission, which is not suitable for signal acquisition and tracking. Other signal components are required to assist the demodulation of CSK modulated signal. To solve this problem, this paper extends the definition of CSK modulated signal, and on this basis, proposes a low complexity acquisition and tracking method for the CSK modulated signal. This method can acquire and track the CSK modulated signal directly without relying on the extra signal components. Theoretical analysis and simulation results verify the effectiveness of the proposed method. Compared with BPSK signal in terms of the acquisition and tracking performance, the direct acquisition and tracking performance of CSK modulated signal is degraded. However, the performance of CSK modulated signal can be compensated by coherent accumulation. In addition, CSK modulated signal does not rely on other signal components for acquisition and tracking, which enhances significantly the independence of receiving CSK modulated signal.KeywordsHigh data rateCSK modulated signalsLow complexityCode tracking errorGNSS